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Lecture 3

EESA06H3 Lecture Notes - Lecture 3: Ophiolite, Syenite


Department
Environmental Science
Course Code
EESA06H3
Professor
Nick Eyles
Lecture
3

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Introduction to Planet Earth
Lecture 03-Quiz #2
Earth history is the history of the oceans
Pangea is the supercontinent 225 million years ago
Continental crust, continents eventually domes/inflate upwards because underneath theres hot,
mantle, plastic rock rising because it is warming.(PLUME) This develops into triple junctions
which are three major fractures.
In Egypt, the arms are called a Rift and if you look at the area of the rift, it is usually going down
and subsiding
The evolution of the triple junction, only one rift opens up and develops into an ocean so we are
able to identify Failed Rifts due to oasis?
Failed rifts are usually filled with sediments and great for oiling gas, because you get a lot of
organic materials such as deltas. It gets cooked and develops hydracarbs.
Petroleum geologists are interested in failed rifts
The Ottawa and St. Lawrence river rifts are both examples of failed rifts
Old rifts might become reactivated and become earthquakes
East Africa: stage one of rift widening and will become a mid ocean ridge
North and into Egypt: Stage 2; red sea which is misnamed because in fact, it is a small ocean that
will widen
Oceans have mid ocean ridges along its center line and oceans are widening all the time but seas
doesnt
The east African rift is where the African plate is being torn apart
The horn of Africa, aka the Somalia plate Is going to break away from Africa and become a little
continental crust
East Africa is the location of a major triple junction; red sea and gulf of Aden
The opening of an ocean forces plates apart
The Arabian plate moves north upon the opening of the red sea
Typical scenery of the east African rift
oFissures are seen and magma comes up the fissures which results in fissure eruptions
oThen we generate either flood basalts which builds an ocean floor
oThere are lots of volcanic cones and ash and craters
Karriandusi: homo habilis, the handy man, 650cc
Many of the major steps in human evolution occurs when the lakes are at their maximum size
because the environment is filled with foods and rich eco system
AFAR triangle, below Arabian plate. This is where Lucy comes from
oRight in the triple junction
oNew ocean floors built
oIt is the driest and hottest areas
oDanakil dessert
oWest of the AFAR triangle is the highlands
Shield volcano which have low slope angles and are not pointy
oThe lava that comes out flow and are characterized by basalt eruptions
Fissure basalts where you are building oceanic crust
The flat volcanoes can release gas easily but the pointy ones has stiffer magma so gas doesnt come
out as readily and they only come out during major eruptions
Gas that causes Deccan lavas which results in extinctions.
280mya major extinction with major eruptions in the west India
Egypt, green belt: Nile river
oNarrow river, that flows through desserts
www.notesolution.com
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